Nucleation and Growth of Stratospheric Aerosols

Despite early evidence of the presence of small particles in regions above the troposphere, it was only about two decades ago that the existence of a globally distributed, temporally persistent, stratospheric aerosol layer was established. Early twilight measurements by Gruner Kleinert and Gruner provided evidence that aerosols exist above the tropopause, but the first careful systematic direct measurements of the change in aerosol concentration with altitude were reported by Junge et al. Their in situ measurements showed the aerosol concentration to decrease monotonically up to and through the tropopause, a fact both expected and confirmed by other investigators.